1. Field of the Invention
The present invention relates to a disc brake apparatus for motor vehicle and in particular to a spring means incorporated in the disc brake apparatus to exert resilient forces to brake pad assemblies.
2. Description of the Prior Art
There has been hitherto known a floating caliper type disc brake apparatus in which a caliper having a pair of depending arms is positioned to streaddle over and across a brake disc mounted on an axle of a motor vehicle and mounted on a stationary member to be movable relative and in parallel thereto. The stationary member in turn is fixedly secured to a stationary portion of the vehicle and has guide grooves formed in the inner wall at leading and trailing sides as viewed in the rotating direction of the disc brake. A pair of brake pad assemblies are disposed at both sides of the brake disc and suspended by the guide grooves so as to be moved toward and away from the brake disc. To this end, each of the brake pad assemblies is formed with a pair of lateral projections adapted to be slidably engaged in the guide grooves.
The disc brake apparatus of the above type has many disadvantages. In the first place, when the brake apparatus is used under unfavorable conditions, the braking plate of the pad assembly as well as the guide grooves tend to be incrusted with rust, as the result of which smooth movement of the brake pad assemblies is disturbed, partial adhesion of the brake pad to the brake disc will occur, the pad will undergo non-uniform abrasion and so forth. As an attempt to obviate such drawback, the width of guide groove is increased with a large clearance. However, this attempt will then involve other difficulties. Namely, various noises are produced. For example, rattling of the brake pad assemblies occurs during the normal running of the vehicle. Upon application of brake, a so-called clonk noise is produced due to the fact that the backing plate of the brake pad assembly strikes at the torque receiving portion of the stationary member. Further, since the brake pad assemblies are not positively retracted while brake is under a released condition, draggling of the pad by the brake disc as well as generation of the squeaking noise often occur.